1. Field of the Invention
The present invention relates to a method of manufacturing a stator of a rotating electric machine, such as an alternating current (AC) generator, for installation onboard a vehicle. More particularly, the invention is concerned with shaping of end portions of stator windings.
2. Description of the Background Art
There is a growing need today for compact, high-power rotating electric machines, such as AC generators for vehicles. In particular, it is desired to lay electrical conductors in a magnetic circuit of a stator with an increased space factor and to neatly shape and arrange coil end portions of stator windings at a higher density.
A previous approach to meeting these requirements is found in Japanese Patent Application Publication No. 2002-176752 (corresponding to U.S. Pat. No. 6,376,961 to Murakami et al), for example, in which stator windings are configured by combining a plurality of winding assemblies each of which is formed by bending multiple strip conductor elements together in order to produce a stator in compact size.
Another previous approach is a coil shaping method disclosed in Japanese Patent Application Publication No. 2004-135438, in which end portions of multiple coil elements projecting from successive slots formed in an annular pattern in a rotor (or stator) are fitted into recesses of a twisting jig and bent at the same time.
Still another previous approach is a conductor end shaping method for forming end portions of multiple stator coils of a rotating electric machine that is shown in Japanese Patent Application Publication No. 1996-205487. In the conductor end shaping method of this approach, a plurality of coil end portions extending from a stator in an annular pattern are sandwiched by a pair of flat or circular opposed shaping members and are formed into a specific shape by application of a mechanical force by means of a movable pressing member.
According to the approach of Japanese Patent Application Publication No. 2002-176752 in which multiple strip conductor elements aligned side by side are shaped into coils, end portions of the multiple strip conductor elements, or line conductors, are shaped to configure terminal leads for connection to specific other conductors. If the end portions of the line conductors are shaped together simultaneously in a plane in which the conductor end portions are parallel-aligned close to one another, the individual conductor end portions will be damaged by mutual friction depending on the direction of bending. It is particularly difficult to avoid damage to the line conductors when the end portions thereof are to be shaped into bent form in a plane which does not make any angle with the plane in which the end portions are parallel-aligned, or in the same plane as the line conductor alignment plane. Although the multiple conductor end portions might be individually bent, and not all together, to prevent damaging, it is inefficient and time-consuming to individually shape a large number of line conductors.
According to the coil shaping method of Japanese Patent Application Publication No. 2004-135438, straight portions of the individual coil elements are placed in the slots formed in the rotor (or stator) and the end portions of the coil elements are bent with a twist at points where the coil elements just stick out of the slots. In this coil shaping method, cuffs are fitted between the coil elements arranged side by side and the large number of coil elements are twisted all together. This method requires extra processes related to the cuffs, including insertion thereof, and complex operation performed by using a complicated twisting jig having a large number of positioning parts tightly arranged side by side for twisting the parallel-aligned coil elements.
According to the conductor end shaping method of Japanese Patent Application Publication No. 1996-205487, the multiple coil end portions are sandwiched by the two facing shaping members which are made movable, and then shaped and gathered together. It is therefore inevitable to avoid mutual friction of individual conductors.